1-Pentene, 5-bromo- → 2,7-Nonanediyl dibutyrate

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FIG. 5 illustrates the scheme for the synthesis of field-active (2S,7S)2,7-nonanediyl dibutyrate (14): S-propylene oxide (6) (Fluka Chemika-Biochemika, Buchs, Switzerland) was coupled at −20° C. with Grignard reagent 7 in the presence of 0.1 equivalents of a CuI catalyst. Resulting (2S)-8-octen-2-ol (8) was oxidized by m-chloroperoxybenzoic acid (Aldrich Chemical Co.) to the terminal epoxide 9. Hydrolytic kinetic resolution of 9 with Co(II) salen (Jacobsen's) catalyst (R,R)N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminoc (10) (Aldrich Chemical Co.) (24, 25) afforded 2(R),7(S)-1,2-epoxy-7-hydroxyoctane (11), which was separated from unwanted 1,2(S),7(S)-octanetriol (12) by silica flash chromatography [hexane: ether (1:1), then ether as eluents]. Ring opening of 11 with excess of methylmagnesium bromide (Aldrich Chemical Co.) and catalytic amounts of Cul yielded (2S,7S)-2,7-nonanediol (13) which was esterified to (2S,7S)-2,7-nonanediol dibutyrate [14; 77% enantiomeric excess (ee) as determined by chiral GC; 37% overall yield]. GC-MS and NMR data of 14 were consistent with those of 5 (FIG. 4). The remaining 3 stereoisomers of diester 5 were synthesized from (S)- or (R)-propylene oxide (Fluka Chemika-Biochemika) and 5-bromo-pentene (Aldrich Chemical Co.), again by hydrolytic kinetic resolution of terminal epoxide intermediates, with ee of end products ranging between 73-85%.

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